Answer: Sounds as though the root system has grown into some hardpan and can't grow any larger. If the tree is important to you you might be able to rent an auger to loosen the soil beneath the tree and then add some sand or compost into the holes you make. This will be only a temporary fix - you will have to be repeat the process in a few years. Or, you can dig the tree and plant it in a different spot in your landscape. Wish I had more ideas to share with you!
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